1. Field of the Invention
Embodiments of the invention relate to the storage and transport of solids and liquids. Preferred embodiment relate to temporary storage of water and to water storage devices in the field of hydrocarbon extraction.
2. Description of the Related Art
Many industries require the use of large volumes of water, sand, or other materials. In some cases the need for storing these materials, or in fact the entire facility creating the need for storing these materials, is transitory. Although the remainder of this background will be discussed in terms of the storage of water, those of skill in the art will recognize, with the benefit of this disclosure, that similar challenges exist in many industries and for storage of many materials, including but not limited to sand, gravel, carbon dust, and concrete, or for liquids that may not be water. The claimed invention may solve one or more problems associated with storage of those and other materials.
One particular industry that may require large volumes of water is the extraction of hydrocarbons from underground deposits. For example, to obtain oil from “tar sands” one may engage in “steam assisted gravity drainage,” which requires many volumes of high-quality water for each volume of oil that is obtained. Water is also important to the “hydraulic fracturing” (or “fracking”) process that may be used to obtain natural gas from shale.
In many cases, the water that is used for hydrocarbon extraction is re-used multiple times, resulting in benefits both to the cost of operations and to the environment. In most situations this requires that water be stored at or convenient to the facility where extraction occurs.
Very often the quality of water after use decreases to the point that purification is required. This may be necessary for environmental reasons (for example, for responsible and compliant disposal) or for reasons related to the further use of the water (for example, as high quality steam).
When water use and purification take place at many different locations (for example, as it does in the fracking process), building and maintaining water purification facilities at all of the locations where water is used and purified can be expensive and inefficient. This is particularly the case where the water use and purification are only necessary for a short period of time, for example during the establishment of a wellhead. Having a large number of separate facilities requires transport of a potentially significant number of small amounts of material. For example, water purification that includes liquid concentration or zero liquid discharge may result in liquid or solid byproducts. There may be a need to collect and store these byproducts for further use, processing, or disposal.
One way that storage, purification, or treatment of water for a large number of sites may be accomplished is to build one or more large purification facilities in reasonable proximity to the sites of use and re-use. This allows the use of economies of scale in the production of the facilities and reduces the need for transport of waste products, which may be accumulated and disposed of together rather than gathered from multiple sites.
One substantial drawback to the use of a single large site for purification or storage is the need to transport the water to be purified to and from the sites of use and re-use. Sometimes the capacity of a facility is too low to handle a substantial influx of water and the water must be stored on-site as it awaits purification. In other cases a large amount of purified water must be stored prior to or after distribution to a site in need of water. In some situations the water is required to sit for substantial periods of time in retaining ponds.
Typically water, both before and after purification, is transported either by pipeline or by tanker truck. Pipelines are expensive to produce and can have an appreciable environmental impact. Tanker trucks are more useful, but use of a truck to store water at both the purification facility and at the use site is an inefficient use of the tanker truck resource. Transport of an empty tanker truck to provide additional storage volume is also inefficient. In some cases the water is transported by a “fixed axle tank,” also known as a “frac tank,” which may be placed on-site and used to store water until the completion of a project.
After the project has been completed the frac tanks or storage tanks may be hauled away, one at a time, for long-term storage or more likely to the next job. This can be inefficient because significant time and effort may be put to hauling empty tanks, one at a time, to and from job sites. In addition to the inefficiencies that are introduced, this procedure may significantly increase the truck traffic one roads associated with extraction sites, as multiple separate trucks are required to remove the frac tanks.
Frac tanks and the like have other disadvantages. For example, due to requirements that they not be overweight or over height, frac tanks have limited storage volumes. Because frac tanks are considered parts of vehicles, they require separate axles, registrations, lights, and permits that all increase the cost of use of the tanks. All of these things increase the cost and complexity of the tanks.
The frac tanks and other water storage tanks also offer substantial challenges related to cleaning the tanks. Chemicals that are used in cleaning the tanks may be caustic or acidic, and in the case of covered tanks the only effective means of cleaning might be for access by a cleaning technician.
As an alternative to frac tanks, some water storage and purification operations establish large ponds or impoundments. Creation and maintenance of these impoundments requires significant construction activity, including grading, leveling, and other ground operations. Location of a pond in-ground makes repair or drainage more difficult in the event of a leak or other failure. When water storage is no longer needed at a site, the impoundments must be filled or otherwise disposed of. More recently, many government entities have begun more stringently regulating impoundments due to their perceived risk for environmental disturbance. This has further increased the cost of installation and use of ponds and impoundments.
Although the prior discussion has focused on the challenges of storage of water, many other commonly used substances present their own storage challenges. For example, an entity may wish to use temporary storage for sand, gravel, carbon dust, or concrete, or for liquids that may not be water.